1. Field of the Invention
The present invention relates generally to the field of telecommunications. More particularly, the present invention relates to systems and methods for detecting errors that cause inefficient telephone network operation.
2. Background of Invention
SS7 is an out-of-band signaling system for the exchange of call-related information between network switching offices, in support of voice and nonvoice services. SS7 messages are exchanged between network elements over bidirectional channels called signaling links. SS7 messaging allows flexibility in providing telephone services. Numerous services such as caller ID, call forwarding, and call conferencing are made possible or greatly enhanced by SS7 messaging. However, SS7 messaging can also give rise to a number of network inefficiencies and trouble conditions. For example, invalid conditions can that consume telephone network resources without providing any benefit to the telephone network. Valid, but undesirable telecommunications events, can waste network resources. Examples of these conditions include call looping, misrouted traffic, unreported mass calling, and excessive redialing.
A call looping condition occurs when a telephone call originated by a calling party to a called party loops between an originating end office and a terminating end office one or more times. Such looping conditions can occur for a number of reasons. One common reason is errors in translations tables that are provisioned in end offices of the telephone network.
A common source of call looping occurs when a first telephone company uses a second telephone company to perform some or all of the first telephone company's call routing. The second telephone company routes its own numbers as well as those numbers sent to it by the first telephone company according to routing tables established in a switch of the second telephone company.
If the first telephone company incorrectly activates an NPA-NXX, a call looping condition can occur. For example, the first telephone might activate a particular NPA-NXX for testing purposes, but not isolate it from the rest of the system. In that case, if a subscriber of the first telephone company misdials a telephone number and dials the NPA-NXX that was activated for testing purpose, the second telephone company would not have been previously advised that it was responsible for routing the NPA-NXX. As a result, the second company's routing tables would indicate that the first telephone company is responsible for routing the telephone call. When the second telephone company receives the NPA-NXX for routing, it consults its routing tables, and sees that the NPA-NXX is assigned to the first telephone company. As a result, it will return the telephone call to the first telephone company for routing. The first telephone company receives the telephone call, and sends it back to the second telephone company for routing. The call is sent back on another trunk, without releasing the first trunk as the call has not been established. This process continues, thereby creating a call loop.
Moreover, multiple trunks are devoted to the looping calls, resulting in inefficiency in the network. For example, when all lines in the trunk are used, the looping condition results in a reorder, meaning the calling party hears a busy signal, and has to redial the called number. Moreover, if the looping calls ties up all the trunks provisioned for the first telephone company then for the duration of the looping call, subscribers of the first telephone company are not be able to make any outbound calls. Often such looping conditions go undetected, because a call could ultimately be routed to the desired called party after several looping iterations. As a result, calling parties do not complain about inability to make calls.
A misrouted traffic condition occurs when a call originated by a calling party to a called party is directed to one or more tandem switches that are not normally involved in completing the call. For example, in a metropolitan area that has five tandem switches, namely, Tandem Switches A through E, a call originating from an originating end office associated with Tandem Switch A to a terminating end office associated with Tandem Switch E desirably uses a trunk linking Tandem Switch A to Tandem Switch E. The misrouted traffic condition occurs when Tandem Switch A, instead of routing the call to Tandem Switch E, misroutes the call to one or more of Tandem Switches B, C, and D. For example, the call may be misrouted such that it “snakes” from Tandem Switch A to Tandem Switch B, from Tandem Switch B to Tandem Switch C, from Tandem Switch C to Tandem Switch D, and finally from Tandem Switch D to Tandem Switch E, using up resources of four trunks, rather than just one. This type of misrouted traffic condition is sometimes referred to as a snaking condition.
A mass calling event occurs when multiple calling parties call a common called party simultaneously, or within a short period of time. One example of such mass calling event is associated with radio station call-ins. For example, when a radio station conducts a survey or a contest during which the general public is invited to call the radio station immediately or within a specific time frame, thousands of telephone calls are originated by the radio station's listeners. As known in the art, such mass calling of a common called party causes significant stress to a telephone company's network, particularly if the radio station does not warn the telephone company ahead of time. Such mass calling events can, among other things, aggravate the call looping and misrouted traffic conditions described above.
An excessive redialing event occurs when a calling party, within a relatively short time frame, repeatedly dials one or more called numbers. For example, excessive redialing can occur when a calling party repeatedly dials the same called number until connected. Redialing can be accomplished either manually or by invoking a feature of the telephone set used by the calling party. Excessive redialing can also occur when the calling party sequentially dials a number of called numbers. This can happen, for example, during a telemarketing campaign in which a computer is used to dial a large number of potential customers' telephone numbers. As known in the art, such excessive redialing causes significant stress to the telephone company's network. Accordingly, these invalid and undesirable conditions use up valuable network resources. Moreover, the cost to telephone companies to diagnose and repair such problems can be significant.
A conventional way to prevent the call looping condition described above is to use a switch-based “hop counter.” Such a switch-based hope counter ensures that a message is not excessively delayed in arriving at the destination. The basic operation of the hop counter is as follows. A telephone network provisions a hop counter at a switch. The hop count is set to a count (e.g., 10) to track the number of times a particular call is looped through the switch. Each time a call is looped back to the switch, the hop counter count is decremented by one. If the hop counter count reaches 0 the call is dropped to prevent an excessive looping condition. As known in the art, the hop counter does not help detect the root cause of the looping condition. For example, the hop counter technology that exists today is not capable of finding errors in translation tables which may cause the looping condition. Moreover, the hop counter technology is not available to all telephone companies. As a result, these telephone companies cannot prevent call looping using a hop counter.